seawater scaling problem 1

[hskk]

Hi guy,

I have a problem using seawater as a cooling media. In the case, the flow of seawater need to be minimised causing the outlet temp to increase. As such, scaling become a problem when the outlet temp reaching above 40 C. Someone has suggested to use 90/10 CuNi tube, does anyone know how high can be the outlet temp of seawater without scaling? Shell & tube hex is using.

Thanks

 

[cub3bead]

Calculate the Stiff Davis Saturation Index to detrmine the scaling tendency of your water. You may have to feed an acid to lower the pH or an antiscalant and dispersant to minimize scaling.

90/10 CuNi won't help with the scaling problem, it is, however, a material suitable for use in seawater heat exchange systems. 70/30 CuNi, titanium, duplex stainless steel, etc. are also suitable for this service.

 

[hskk]

Thanks for your comments.

May I know the equation to calculate the Stiff Davis Saturation Index or can you tell me where to get the equation?

Thanks

 

[cub3bead]

Look at ASTM D 4582 - Practice for Calculation and Adjustment of the Stiff and Davis Stability Index for Reverse Osmosis. You should be able to adapt the calculation to your situation.

 

[EdStainless]

If you have too much cooling you need to bypass some of your process around the HX. NEVER resort to reducing cooling water flow. It will assure that you will foul, scale and cut short the life of the HX.
For sewater cooling there are a number of suitable alloys. You can use Ti (CP Gr2), a superferritic (S44660)or superduplex, 70/30, or a 6%Mo superaustenitic (but in todays market the price for this will be outragous).
These alloys all have upper temp limits, and fouling makes things worse. Look hard at what you can do to get your flow rates up.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

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